1. Field of the Invention
The present invention relates to a network system in which a client device is connected to a server and particularly relates to a network system which enables a user to look for a still picture which the user wishes to view in numerous still pictures stored in the server from the client device.
2. Description of the Related Art
Conventionally, a network system conforming to DLNA guideline (Digital Living Network Alliance guideline, which is a technical specification to connect audio-visual (AV) equipments, personal computers, and information appliances to each other for cooperative usage by using home LAN (Local Area Network) (home network), abbreviated as DLNA hereinafter) is known as the above network system. In the DLNA, a DMS (Digital Media Server) which records, stores, and provides contents is provided as the server, and a DMP (Digital Media Player) which reproduces the contents of the DMS is provided as the client. Once hooked up to a network, both DMS and DMP are operational, and the DMP finds the DMS in the network and obtains a list of the available contents automatically. Thus, once the above DLNA compliant equipment is hooked up to the network, the contents of other equipments are available automatically. For example, a network attached storages, which are file service machines, personal computers, DVD/HDD recorders, and video cameras can be used as the DMS, and AV equipments such as television receivers, notebook computers, and personal digital assistants (PDA) can be used as the DMP, and moreover, one equipment may have functions of both DMS and DMP.
Each still picture file stored in the above DMS is normally provided with a file name, which is automatically created in each digital camera for each data of still pictures which are taken with the digital camera, and is stored in a storage medium such as IC card of the digital camera temporarily, and subsequently, transmitted from the storage medium to be stored in the DMS.
The digital camera automatically creates the file name in accordance with DCF (Design rule for Camera File system) and records the still picture file for the still pictures, which are taken with the digital camera, in the storage medium. In the DCF, each digital camera manufacturer adds an arbitrary character to three directory numbers to set a directory name and arranges three arbitrary characters, four directory numbers, and an extension sequentially to set the file name. Moreover, data of the above file include a photographing date and time, so that a photographing date and time of each still picture is stored in the file data.
Normally, it is uncommon for the user to determine the directory name and a hierarchy of the pictures by himself/herself when storing the still picture taken with the digital camera in the server, and the still picture file for the still pictures, which are taken with the digital camera, is often stored in the recording medium with the directory name which is automatically created in the digital camera when taking the picture.
In the DMP connected to the network of the above DLNA, when the user wishes to view a still picture of a photograph, which is taken with the digital camera, in the contents which are stored in each DMS connected to the network, a search process shown in FIG. 7, for example, is performed: the user operates the DMP to specify the DMS (S101), further specify the directory of the still picture stored in the specified DMS (S102), and search the directory whose name is identical with that of the directory created automatically in the digital camera and move down the hierarchy sequentially for search, so that the still picture which the user wishes to view is found and displayed (S103). However, in the above search process, when still pictures which are taken with digital cameras of different manufacturers are mixedly stored in the server, for example, it is difficult to determine what types of the still pictures are in each directory based on simply the directory names created in each digital camera.
Consequently, in the conventional process for searching the still picture, the user is required to remember which directory the desired still picture is stored in the DMS, and unless the user remembers the directory in which the desired still picture is stored, it is difficult to search the desired still picture easily. Moreover, because capacities of a storage medium of the picture data such as a memory card using a nonvolatile memory, a HDD (hard disk) using magnetic disks, and so on get larger, a total amount of the still picture files which can be stored in the respective storage mediums in the digital camera and the server increases dramatically. As a result, the time for searching the desired still picture file in many still picture files stored in the storage medium gets even longer, so that a means for searching the desired still picture more easily is coveted.
As shown in Japanese Laid-Open Patent Publication No. 2004-96582, there is a known picture file management method which creates a directory in a storage medium in accordance with a date on which pictures in the picture files are taken (photographing date), arranges number symbols which represent the photographing date so as to set a name of the directory for each directory, and stores the picture file of the picture whose photographing dates corresponds to the directory. This picture file management method enables an easy storage management of the picture file. However, unless the user remembers which picture is taken on the photographing date, the desired picture file cannot easily be found just by seeing the name of the picture file which is made up of the number symbols which represent the photographing date.
There is a known recording apparatus which encodes data as an encoded data of a predetermined codec level and codec class to classify a codec with a predetermined encoding system and makes a storage medium store the encoded data as a file whose name represents the codec level of the encoded data (refer to Japanese Laid-Open Patent Publication No. 2006-165918, for example). However, in this apparatus, when the name of the encoded data file in a directory which includes letters representing the codec encoding system is displayed, a thumbnail is located in an area immediately in front of the file name, and the presence and absence of this thumbnail shows whether or not the encoded data can be decoded by the codec of the apparatus, so that it is not easy to find the desired still picture file only by the directory name.
There is a known digital camera which transmits picture data taken with the digital camera to a personal computer in a home network and a server on Internet via a network so that the picture data are stored in the personal computer and the server and the picture data in the digital camera is stored more certainly (refer to Japanese Laid-Open Patent Publication No. 2003-319309, for example). In this digital camera, the still pictures are stored in a holder (directory) whose name includes a photographing date, however, the desired still picture cannot immediately be found just by seeing the holder name.